Recording sheet with ink receptive layer and coating liquid for forming ink receptive layer

ABSTRACT

A recording sheet with an ink-receptive layer which can be used not only for dye type inks but also for pigment type inks is provided. Also provided is a coating liquid for forming an ink-receptive layer. The recording sheet with an ink-receptive layer includes a substrate sheet and an ink-receptive layer formed thereon, wherein the ink-receptive layer includes (i) fibrous crystalline particles on surfaces of which a cationic hydrated metal compound is supported and (ii) a binder. The fibrous crystalline particles have an average fiber diameter (D) of 0.1 to 2 μm, an average fiber length (L) of 1 to 200 μm and a ratio (aspect ratio) of an average fiber length (L) to an average fiber diameter (D) of 5 to 500.

TECHNICAL FIELD

The present invention relates to a recording sheet with an ink-receptivelayer. More particularly, the invention relates to a recording sheetwith an ink-receptive layer on which printing can be clearly made withuniform density, which is capable of firmly fixing dye or the like andwhich is capable of providing a print having excellent water resistance,weathering resistance and fading resistance and having satisfactorystrength.

The present invention also relates to a coating liquid for forming theabove-mentioned ink-receptive layer.

BACKGROUND ART

Printing by an ink jet method has rapidly spread and used for variouspurposes because printing of the same image quality as in theconventional multi-color printing or color photographic system isfeasible, speeding up or multi-coloring is easily made, and the cost islower than the conventional printing methods in case of a small numberof sheets to be printed.

In the printing by the ink jet method, a recording sheet having on asubstrate sheet an ink-receptive layer formed by coating the substratesheet with a water-soluble polymer such as polyvinyl alcohol isemployed, and on the sheet, printing is carried out by the use of awater base ink. The resulting print, however, has insufficient waterresistance, and there is a problem of lowering of image quality in thecase where the print is placed in environment of high moisture or iswetted by water. Further, there is another problem that an image of highsharpness and high precision cannot be obtained because the recordingsheet used has insufficient ink absorption characteristics.

To solve such problems, a recording sheet wherein an ink-receptive layercontaining fine particles of silica, alumina or the like is formed on asubstrate sheet is proposed.

For example, in Japanese Patent Laid-Open Publication No. 149475/1987, arecording sheet wherein an ink-receptive layer containing sphericalparticles of silica or the like having an average particle diameter of 1to 50 μm is formed is described. In Japanese Patent Publication No.24906/1991, a recording medium having an ink-receptive layer containingcationic hydrated aluminum oxide is described. In Japanese PatentPublication No. 19037/1992, a recording medium having a receptive layercontaining cationic colloidal silica is described. In Japanese PatentLaid-Open Publication No. 115984/1992, a recording sheet wherein a layerof pseudo-boehmite alumina is formed on a substrate and a layer ofporous silica is further provided thereon is described. In JapanesePatent Laid-Open Publication No. 55829/1994, a recording sheet having ona substrate a layer of porous silica particles having an averageparticle diameter of 2 to 50 μm, an average pore diameter of 8 to 50 nmand a pore volume of 0.8 to 2.5 cc/g and further having thereon apseudo-boehmite porous layer obtained by drying an alumina sol isdescribed.

Most of these recording sheets are intended for printing using dye typeinks, but because the dye type inks have poor weathering resistance, theresulting prints have disadvantages such as discoloration or decoloringcaused by exposure to ultraviolet light, oxygen, ozone or the like, andsuch disadvantages are markedly observed especially when the prints areused outdoors.

Therefore, pigment type inks having excellent weathering resistance cameto be used even in the ink jet printing method.

Pigment particles, however, are particles usually having diameters of 10to 500 nm, and the conventional ink-receptive layer does not have porescapable of effectively absorbing such large particles, so that thereresides problems such that the pigment particles remain on theink-receptive layer surface without being absorbed by the ink-receptivelayer, the ink-receptive layer exhibits insufficient water resistance,and the pigment particles are removed by rubbing to cause crocking.

The present invention is intended to solve such problems associated withthe prior art as described above, and it is an object of the inventionto provide a recording sheet with an ink-receptive layer which can beused not only for dye type inks but also for pigment type inks, hasexcellent printing properties such that a print free from ink blottingis obtainable and clear printing with uniform density is feasible, isexcellent in water resistance, weathering resistance and fadingresistance and has sufficiently high strength, and a coating liquid forforming an ink-receptive layer.

In particular, it is an object of the invention to provide a recordingsheet with an ink-receptive layer which is desirable for high-speedprinting by an ink jet method and is favorably used also as a recordingsheet, such as white color PET for large size color printer or artpaper, or a recording sheet having no absorption characteristics andneeding transparency, and a coating liquid for forming an ink-receptivelayer.

SUMMARY OF THE INVENTION

The recording sheet with an ink-receptive layer according to the presentinvention is a recording sheet comprising a substrate sheet and anink-receptive layer formed thereon, wherein the ink-receptive layercomprises:

(i) fibrous crystalline particles on surfaces of which a cationichydrated metal compound is supported, and

(ii) a binder.

The fibrous crystalline particles are preferably particles of at leastone substance selected from the group consisting of basic magnesiumsulfate (MgSO₄.5Mg(OH)₂.nH₂O), basic calcium sulfate(CaSO₄.5Ca(OH)₂.nH₂O), basic barium sulfate (BaSO₄.5Ba(OH)₂.nH₂O), basicstrontium sulfate (SrSO₄.5Sr(OH)₂.nH₂O) and calcium silicate(Ca₂SiO₄.nH₂O).

The fibrous crystalline particles preferably have an average fiberdiameter (D) of 0.1 to 2 μm, an average fiber length (L) of 1 to 200 μmand a ratio (aspect ratio) of an average fiber length (L) to an averagefiber diameter (D) of 5 to 500.

The cationic hydrated metal compound is preferably a compoundrepresented by the following formula (1) or a compound obtained from ametal salt represented by the following formula (2):[M₂(OH)_(n)X_((2a-n)/b)]_(m)  (1)[MX_(a/b)]_(m)  (2)

wherein M is a trivalent or higher metallic cation, X is an anion, a isa valence of the metallic cation, b is a valence of the anion, and n andm are numbers satisfying the conditions of 1<n<5, n<2a and 1≦m.

In the cationic hydrated metal compound, M is preferably Al³⁺.

The recording sheet with an ink-receptive layer preferably furthercomprises inorganic fine particles.

The inorganic fine particles are preferably one or more substancesselected from an alumina sol, an alumina gel, a silica sol, a silicagel, a silica-alumina sol, a silica-alumina gel, a zirconia sol, azirconia gel and a clay mineral.

The inorganic fine particles are preferably an alumina sol and/or analumina gel each of which is pseudo-boehmite alumina.

The ink-receptive layer preferably has pores having pore diameters of 30to 2000 nm, and a pore volume of the pores having pore diameters of 30to 2000 nm is preferably in the range of 0.15 to 2.0 ml/g.

The coating liquid for forming an ink-receptive layer according to thepresent invention comprises (i) fibrous crystalline particles onsurfaces of which a cationic hydrated metal compound is supported and(ii) a binder, said fibrous crystalline particles (i) and said binder(ii) being dispersed in a dispersion medium consisting of water and/oran organic solvent.

DETAILED DESCRIPTION OF THE INVENTION Recording Sheet with Ink-ReceptiveLayer

The recording sheet with an ink-receptive layer according to theinvention comprises a substrate sheet and an ink-receptive layer formedon the substrate sheet.

Substrate Sheet

The substrate sheet for use in the invention is not specificallyrestricted, but usually used are film sheets made of resins such as PETand polyvinyl chloride, various papers, steel plates, cloths and thelike.

Ink-Receptive Layer

The ink-receptive layer formed on the substrate sheet comprises (i)fibrous crystalline particles on surfaces of which a cationic hydratedmetal compound is supported (referred to as “cationic hydrated metalcompound-supported fibrous crystalline particles” hereinafter) and (ii)a binder.

(i) Cationic hydrated metal compound-supported fibrous crystallineparticles

In the present invention, fibrous crystalline particles on surfaces ofwhich a cationic hydrated metal compound is supported are employed.

The fibrous crystalline particles for use in the invention have a fiberdiameter (D) of preferably about 0.1 to 2 μm, more preferably 0.5 to 1μm, and a fiber length (L) of preferably about 1 to 200 μm, morepreferably 3 to 100 μm. A ratio (aspect ratio) of a fiber length (L) toa fiber diameter (D) is in the range of preferably 5 to 500, morepreferably 10 to 200.

When such fibrous crystalline particles, particularly fibrouscrystalline particles having a high aspect ratio, are contained, theyare entangled with one another without being densely filled, and poresare easily formed, whereby a porous ink-receptive layer having a porevolume capable of receiving both of a dye type ink and a pigment typeink can be formed. Further, by virtue of such entanglement of thefibrous crystalline particles, strength of the ink-receptive layeritself can be enhanced.

When such fibrous crystalline particles are contained, an ink-receptivelayer having a pore volume capable of receiving both of a dye type inkand a pigment type ink can be formed, and besides, strength of theink-receptive layer itself can be enhanced. By the use of such fibrouscrystalline particles, further, the ink-receptive layer has hightransparency, and a clear print can be obtained.

If the fiber diameter (D) of the fibrous crystalline particles is lessthan 0.1 μm, the pore volume is increased but the strength of theink-receptive layer becomes insufficient, though it depends upon thelength of the fibrous crystalline particles. If the fiber diameter (D)of the fibrous crystalline particles exceeds 2 μm, transparency of theink-receptive layer is lowered, and the resulting print has insufficientclearness.

If the fiber length (L) of the fibrous crystalline particles is lessthan 1 μm, the pore volume becomes insufficient, and the ink absorptionquantity or the ink absorption rate tends to be decreased to lowerprinting performance, though it depends upon the fiber diameter of thefibrous crystalline particles.

If the fiber length (L) of the fibrous crystalline particles exceeds 200μm, the coating liquid obtained has a high viscosity, and it becomesdifficult to control a film thickness.

If the aspect ratio is less than 5, an effect given by the use of thefibrous crystalline particles is not sufficient, that is, the porevolume becomes insufficient, and the ink absorption quantity or the inkabsorption rate tends to be decreased to lower printing performance.

If the aspect ratio exceeds 500, the coating liquid obtained has a highviscosity, and it becomes difficult to control a film thickness.

Such a size of the fibrous particles is determined in the followingmanner. A scanning electron microphotograph (SEM photograph) is taken,then fiber diameters and fiber lengths of 20 particles of the photographare measured, and from average values of the fiber diameters and thefiber lengths, the size is calculated.

The fibrous crystalline particles are not specifically restrictedprovided that they have the aforesaid shape and size, and for example,particles of a basic alkaline earth metal sulfate compound or analkaline earth metal silicate compound are employable. Morespecifically, particles of basic magnesium sulfate(MgSO₄.5Mg(OH)₂.nH₂O), basic calcium sulfate (CaSO₄.5Ca(OH)₂.nH₂O),basic barium sulfate (BaSO₄.5Ba(OH)₂.nH₂O), basic strontium sulfate(SrSO₄.5Sr(OH)₂.nH₂O) and calcium silicate (Ca₂SiO₄.nH₂O) areemployable. Of these, fibrous basic magnesium sulfate is desirably usedbecause it is inexpensive and an ink-receptive layer having large porediameters, a large pore volume and high strength is obtained. Inparticular, an ink-receptive layer having an average pore diameter ofnot less than 30 nm tends to be obtained.

Such a basic alkaline earth metal sulfate compound can be obtained by,for example, subjecting a sulfate of an alkaline earth metal and analkaline earth metal hydroxide to hydrothermal reaction in an autoclaveat a temperature of 100 to 200° C. The size of the fibrous crystallineparticles of the resulting basic alkaline earth metal sulfate compoundcan be controlled by the hydrothermal reaction conditions.

In the present invention, fibrous crystalline particles on surfaces ofwhich a cationic hydrated metal compound is supported are employed. Thecationic hydrated metal compound-supported fibrous crystalline particlescan be obtained specifically by adding a cationic hydrated metalcompound to a dispersion of the fibrous crystalline particles andthereby allowing the surfaces of the particles to support the compound.

As the cationic hydrated metal compound, a compound represented by thefollowing formula (1) is preferably employed.[M₂(OH)_(n)X_((2a-n)/b)]_(m)  (1)wherein M is a trivalent or higher metallic cation, X is an anion, a isa valence of the metallic cation, b is a valence of the anion, and n andm are numbers satisfying the conditions of 1<n<5, n<2a and 1≦m.

The metallic cation is preferably a trivalent or tetravalent metalliccation, and is more preferably a metallic cation of Al³⁺, Zr⁴⁺, Ti⁴⁺,Ga⁴⁺ or the like. The anion is, for example, a halogen ion, a sulfuricacid ion, a nitric acid ion or an organic anion.

The cationic hydrated metal compound can be prepared by a conventionalprocess. For example, the compound can be obtained by a processcomprising dissolving aluminum hydroxide in hydrochloric acid underpressure or in the presence of a dissolving assistant to preparealuminum chloride and aging it in the presence of a polymerizationpromoter such as sulfuric acid.

A dispersion obtained by dispersing the fibrous crystalline particles ina solvent such as water, methanol, ethanol, isopropyl alcohol or a mixedsolvent thereof is mixed with a solution of the cationic hydrated metalcompound to perform reaction. In the reaction, an alkali is added to thedispersion to adjust pH of the dispersion, when needed. Although pH ofthe dispersion varies depending upon the type of the crystalline aluminaparticles used, it has only to be in the range of about 2 to 9. The pHis more preferably in the range of 3 to 6.

It is possible to prepare the cationic hydrated metal compound from ametal salt represented by the following formula (2).

That is to say, instead of the compound represented by the formula (1)or together with the compound represented by the formula (1), an aqueoussolution of a metal salt represented by the following formula (2) isadded to a dispersion of the fibrous crystalline particles, then analkali is added, and pH of the dispersion is adjusted in the aboverange, whereby fibrous crystalline particles on surfaces of which acationic hydrated metal compound is supported can be obtained.[MX_(a/b)]_(m)  (2)wherein M, X, a and b have the same meanings as in the aforesaid formula(1).

In the formulas (1) and (2), M is preferably Al³⁺. By the use of such acationic hydrated metal compound or such a metal salt as mentionedabove, the surfaces of the fibrous crystalline particles conspicuouslybecome cationic, and the resulting ink-receptive layer has a highstreaming potential (surface charge quantity). On this account, dye orpigment can be firmly fixed, and hence, the ink-receptive layer exhibitsexcellent water resistance.

The amount of the cationic hydrated metal compound supported (amountsupported=amount added; in case of a metal salt represented by theformula (2), amount added; in case of both of (1) and (2), total amount)is in the range of preferably 0.01 to 5 mol, more preferably 0.1 to 2mol, in terms of a metal oxide, based on 1 mol of the fibrouscrystalline particles, such as particles of a basic alkaline earth metalsulfate compound.

If the amount of the compound supported is less than 0.01 mol, theresulting ink-receptive layer has a low streaming potential. Therefore,dye or pigment cannot be firmly fixed, and the ink-receptive layerexhibits insufficient water resistance.

If the amount of the cationic hydrated metal compound based on 1 mol ofthe fibrous crystalline particles exceeds 5 mol, dispersion stability ofthe resulting cationic hydrated metal compound-supported fibrouscrystalline particles tends to be lowered, and when printing is carriedout, dye tends to be adsorbed only on the upper part of theink-receptive layer to lower image quality.

When the cationic hydrated metal compound is added to a dispersion ofthe cationic fibrous crystalline particles to treat the particles, theconcentration of the fibrous crystalline particles is not specificallyrestricted provided that cationic hydrated metal compound-supportedfibrous crystalline particles having a high streaming potential can beobtained, and the concentration is usually in the range of 1 to 30% byweight. The temperature is in the range of 5 to 60° C. In thistreatment, the dispersion has pH of 2 to 7.

The cationic hydrated metal compound-supported fibrous crystallineparticles obtained as above are in the same fibrous state as that of thebasic alkaline earth metal sulfate compound particles.

The cationic hydrated metal compound-supported fibrous crystallineparticles have a streaming potential of preferably 1 to 200 μeq/g, morepreferably 2 to 100 μeq/g.

If the streaming potential of (i) the fibrous crystalline particles onsurfaces of which the cationic hydrated metal compound is supported isless than 1 μeq/g, dye cannot be firmly fixed and the amount of the dyefixed is small, so that water resistance sometimes becomes insufficientor the resulting print sometimes lacks clearness.

If the streaming potential of the cationic hydrated metalcompound-supported fibrous crystalline particles exceeds 200 μeq/g, dyeis fixed locally to the upper part of the receptive layer and cannot befixed to the lower part of the receptive layer, or the pores in theupper part are sometimes choked. On this account, inks are not absorbedor blotting occurs occasionally during multiple printing using differentcolor inks.

The streaming potential of the cationic hydrated metalcompound-supported fibrous crystalline particles can be determined inthe following manner by the use of a streaming potential measuringdevice (manufactured by MUTEC K.K., PCD 03PH).

A water dispersion of cationic hydrated metal compound-supported fibrouscrystalline particles (solids concentration: 1% by weight) is prepared,then to the dispersion is dropwise added an anionic polyelectrolyte(sodium polyethene sulfonate, Pes-Na) until the potential becomes zero,and a charge quantity is calculated from the following formula.q=V×c/wt

V: titer of electrolyte (L)

C: titrant charge concentration (eq/L)

wt: solids weight (g) of cationic hydrated metal compound-supportedfibrous crystalline particles

q: charge quantity (eq/g)

When such cationic hydrated metal compound-supported fibrous crystallineparticles are used, an ink-receptive layer wherein a pore volume ofpores having pore diameters of 30 to 2000 nm is in the range of 0.2 to2.0 ml/g, preferably 0.2 to 1.0 ml/g, can be obtained. Therefore, as theprinting inks, pigment inks can be favorably used in addition to dyeinks. Further, because of high ink absorption rate, the ink-receptivelayer is free from ink blotting and exhibits excellent printingproperties. Moreover, because the particle surface has a high streamingpotential, an ink-receptive layer to which dye can be firmly fixed andwhich is excellent in water resistance, weathering resistance and fadingresistance can be obtained.

In the present invention, the cationic hydrated metal compound-supportedfibrous crystalline particles may be used after their surfaces are madehydrophobic, when needed. When the cationic hydrated metalcompound-supported fibrous crystalline particles are used after theirsurfaces are made hydrophobic, adsorption or permeation of water intothe ink-receptive layer hardly occurs, and water resistance of theink-receptive layer is enhanced.

Although a method to make the cationic hydrated metal compound-supportedfibrous crystalline particles hydrophobic is not specificallyrestricted, a conventional method such as a method of treating thecationic hydrated metal compound-supported fibrous crystalline particleswith a coupling agent, such as monomethylsilane,monomethyltrimethoxysilane, monomethyltriethoxysilane,dimethyldimethoxysilane, dimethylvinylmethoxysilane,phenyltriethoxysilane, diphenyldimethoxysilane, vinyltrichlorosilane orγ-glycidoxypropyltrimethoxysilane, is available.

Binder

Examples of the binders for use in the invention include polyvinylalcohol, modified polyvinyl alcohol, polyvinyl pyrrolidone, and organiccompounds such as hydrophilic polymers. They may be used after modified.

These binders may be used singly or in combination.

The binder is used in an amount of 5 to 60% by weight, preferably 10 to40% by weight, based on the cationic hydrated metal compound-supportedfibrous crystalline particles, though the amount varies depending uponthe type of the binder used.

If the amount of the binder is less than 5% by weight, adhesion strengthof the ink-receptive layer to the substrate sheet is insufficient andthe ink-receptive layer is liable to peel off, or the ink-receptivelayer has insufficient strength. If the amount of the binder exceeds 60%by weight, the amount of ink received is sometimes decreased, or thewater resistance is sometimes lowered.

The ink-receptive layer may further contain components which are usuallyadded to an ink-receptive layer, for example, antioxidants, organicpolymers, such as celluloses, bio-fibers, inorganic polymers andinorganic fine particles, in addition to the above-mentioned components.

In particular, the ink-receptive layer preferably further containsinorganic fine particles.

The inorganic fine particles are preferably one or more substancesselected from an alumina sol, an alumina gel, a silica sol, a silicagel, a silica-alumina sol, a silica-alumina gel, a zirconia sol, azirconia gel and a clay mineral. The inorganic fine particles areparticularly preferably an alumina sol and/or an alumina gel each ofwhich is pseudo-boehmite alumina.

Process for Forming Ink-Receptive Layer

The process for forming an ink-receptive layer on a substrate sheet isnot specifically restricted provided that an ink-receptive layercomprising (i) fibrous crystalline particles on surfaces of which acationic hydrated metal compound is supported and (ii) a binder isformed, and any of publicly known processes is adoptable. According tothe type of the substrate, a preferred process is adopted.

More specifically, the ink-receptive layer can be formed by coating asubstrate sheet with the later-described coating liquid for forming anink-receptive layer by a spray method, a roll coater method, a bladecoater method, a curtain coater method or the like and then drying thecoated layer.

The substrate sheet may be subjected to primer treatment in advance.

The ink-receptive layer formed as above has pores having pore diametersof usually 30 to 2000 nm, and a pore volume of the pores having porediameters of 30 to 2000 nm is in the range of 0.15 to 2.0 ml/g,preferably 0.2 to 2.0 ml/g, more preferably 0.2 to 1.0 ml/g.

If the pore volume of the pores having pore diameters of 30 to 2000 nmis less than the lower limit of the above range, pigment type ink cannotbe absorbed sufficiently. Therefore, the pigment particles remain on thesurface of the ink-receptive layer, and these pigment particlessometimes separate off by rubbing to cause crocking of the resultingprint. If the pore volume is more than the upper limit of the aboverange, fixability of the pigment particles is lowered or most of thepigment particles gather in the lower part of the ink-receptive layer(in the vicinity of the substrate surface) after printing, and hence,the image sometimes lacks sharpness.

The thickness of the ink-receptive layer formed on the substrate sheetcan be arbitrarily determined according to the thickness of the sheet,purpose of the print, type of the printing ink, etc., but it is desiredto be in the range of usually 5 to 100 μm. If the thickness of theink-receptive layer is less than 5 μm, capacity for ink absorptionbecomes insufficient to cause ink blotting, or color is sometimeslowered when the amount of ink used is decreased. On the other hand, itis difficult to obtain an ink-receptive layer having a thickness of morethan 100 μm by one coating operation, and coating operations of pluraltimes are disadvantages from the economical viewpoint. Further, crazingor peeling sometimes takes place during drying of the coated layer.

In the present invention, the pore volume of the ink-receptive layerformed on the substrate sheet is measured by the following mercurypenetration method.

About 0.2 to 0.3 g of a recording sheet with an ink-receptive layerprepared is placed in a measuring cell (volume: 0.5 cc), and a poredistribution is measured by the use of a QUANTA CHROME AUTOSCAN-60POROSIMETER under the conditions of a mercury contact angle of 130°, amercury surface tension of 473 dyn/cm² and a measuring range of “highpressure”. From the pore distribution measured, a pore volume of poresof 3.4 to 30 nm and a pore volume of pores of 30 to 2000 nm areobtained, and from the weight of the receptive layer in the recordingsheet, a pore volume based on 1 g of the receptive layer is determined.

Coating Liquid for Forming Ink-Receptive Layer

In the coating liquid for forming an ink-receptive layer according tothe invention, (i) the fibrous crystalline particles on surfaces ofwhich a cationic hydrated metal compound is supported and (ii) thebinder are dispersed in a dispersion medium consisting of water and/oran organic solvent.

Examples of the components of the coating liquid include the samesubstances as previously described.

As the organic solvent, isopropyl alcohol, ethanol, butanol or the likecan be used singly or in combination.

The concentration of the cationic hydrated metal compound-supportedfibrous crystalline particles (i) in the coating liquid is properlydetermined according to the coating method used, and it is desired to bein the range of preferably 2 to 40% by weight, particularly preferably 5to 30% by weight. The amount of the binder is in the range of preferably5 to 60% by weight, more preferably 10 to 40% by weight, based on thecationic hydrated metal compound-supported fibrous crystallineparticles.

For the purpose of enhancing adhesion of the ink-receptive layer to thesubstrate sheet or increasing strength and weathering resistance of theink-receptive layer or controlling a pore structure of the ink-receptivelayer, the coating liquid of the invention may contain antioxidants,organic polymers such as celluloses, bio-fibers, inorganic polymers,inorganic fine particles, etc., as previously described.

In the recording sheet with an ink-receptive layer according to theinvention, the ink-receptive layer comprises (i) fibrous crystallineparticles on surfaces of which a cationic hydrated metal compound issupported and (ii) a binder. Therefore, the pore volume of pores havinga specific pore diameter range is large and the surface has a highstreaming potential. On this account, the ink-receptive layer exhibits ahigh ink absorption rate, and dyes can be firmly fixed to the layer, sothat the ink-receptive layer has excellent water resistance, weatheringresistance and heat resistance. Further, because the cationic hydratedmetal compound-supported fibrous crystalline particles are fibrous, theink-receptive layer has high strength. Furthermore, the recording sheetwith such an ink-receptive layer exhibits excellent printing propertiesand enables clear printing even if printing is carried out using variousinks, irrespective of the printing method. Moreover, the recording sheetwith such an ink-receptive layer is favorable also for printing usingpigment type inks.

By the use of the coating liquid for forming an ink-receptive layeraccording to the invention, an ink-receptive layer having such excellentproperties as described above can be formed.

EXAMPLES

The present invention is further described with reference to thefollowing examples, but it should be construed that the invention is inno way limited to or by those examples.

Example 1 Preparation of Cationic Hydrated Metal Compound-SupportedFibrous Crystalline Particles (1) for Forming Ink-Receptive Layer

In a 13.8 kg of pure water, 2 kg of basic magnesium sulfate (availablefrom Ube Materials Industries, Ltd., Mos Hige, solids concentration: 84%by weight, average fiber diameter: 0.75 μm, average fiber length: 12 μm)as a basic alkaline earth metal sulfate compound was dispersed toprepare a slurry. To the slurry, 679.3 g of a cationic hydrated metalcompound (available from Oki Kagaku K.K., PAC #1000, Al₂O₃: 23.34% byweight, Cl: 8.06% by weight, basicity: 83.44%) was added so that themolar ratio to the basic magnesium sulfate should become 0.36, followedby stirring at 25° C. for 60 minutes. Then, the solids were separated byfiltration, dried at 110° C. for 16 hours and pulverized by a mixer(manufactured by Hitachi, Ltd., VA-W-27) to prepare a powder of cationichydrated metal compound-supported fibrous crystalline particles (1) forforming an ink-receptive layer. In the pulverization using a mixer, thefibrous crystalline particles were hardly pulverized, and aggregatesthereof were disaggregated.

The powder of the cationic hydrated metal compound-supported fibrouscrystalline particles (1) had an average fiber diameter of 0.75 μm, anaverage fiber length of 12 μm and a streaming potential of 31 μeq/g.

Preparation of Coating Liquid (1) for Forming Ink-Receptive Layer

86 Parts by weight of a dispersion obtained by dispersing theabove-obtained powder of the cationic hydrated metal compound-supportedfibrous crystalline particles (1) in water so that the solidsconcentration should become 11.4% by weight and 14 parts by weight of apolyvinyl alcohol aqueous solution having a concentration of 10% byweight were mixed to prepare a coating liquid (1) for forming anink-receptive layer.

Preparation of Recording Sheet (1)

Subsequently, the coating liquid (1) was applied onto a PET film by theuse of a bar coater, dried and then subjected to heat treatment at 140°C. to prepare a recording sheet (1). The ink-receptive layer had athickness of 30 μm. The pore volume of the ink-receptive layer wasmeasured by the aforesaid mercury penetration method.

Then, printing was carried out on the resulting recording sheet (1) inthe following manner, and the print was evaluated.

The results are set forth in Table 1.

Printing

On the resulting recording sheet, a solid pattern W of 2 cm square wasprinted by an ink jet printer (manufactured by GRAPHTEC Co., Masterjet)using genuine dye inks and pigment inks. Colors of magenta, black, cyanand yellow were used, and for each printing, an output power was alteredto change density.

Density

The density was measured by a color reflection densitometer(manufactured by Nippon Denshoku Industries Co., Ltd., KRD-2200). Whenthe density is not less than 1.2, the print is employable without anyproblem.

Blotting

The shape of each printed dot was observed by a microscope, andevaluation was carried out according to the following criteria.

AA: The dot is completely circular, and no blot is observed.

BB: The dot is circular, but a slight blot is observed.

CC: The dot is circular, but a marked blot is observed.

Drying Rate

Different two-color dots overlapping each other were observed by amicroscope to examine mixing of colors, and evaluation was carried outaccording to the following criteria.

AA: Mixing of colors is not observed.

BB: Mixing of colors is slightly observed.

CC: Mixing of colors is markedly observed.

Water Resistance

A strip of the resulting print was immersed in water to observe elutionof dye or pigment, and evaluation was carried out according to thefollowing criteria.

AA: No blot is observed.

BB: A blot is slightly observed.

CC: A blot is markedly observed.

DD: Elution of dye or pigment is observed.

Crocking

A printed part of the print using pigment ink was rubbed with a fingerto examine change of image quality and adhesion of the pigment to thefinger. Then, evaluation was carried out according to the followingcriteria.

AA: Change of image quality and adhesion of pigment are not observed.

BB: Change of image quality or adhesion of pigment is observed.

Example 2 Preparation of Cationic Hydrated Metal Compound-SupportedFibrous Crystalline Particles (2) for Forming Ink-Receptive Layer

A powder of cationic hydrated metal compound-supported fibrouscrystalline particles (2) for forming an ink-receptive layer wasprepared in the same manner as in Example 1, except that 905.7 g of acationic hydrated metal compound (available from Oki Kagaku K.K., PAC#1000, Al₂O₃: 23.34% by weight, Cl: 8.06% by weight, basicity: 83.44%)was added so that the molar ratio to the basic magnesium sulfate shouldbecome 0.48. The powder of the cationic hydrated metalcompound-supported fibrous crystalline particles (2) had an averagefiber diameter of 0.75 μm, an average fiber length of 12 μm and astreaming potential of 42 μeq/g.

Preparation of Coating Liquid (2) for Forming Ink-Receptive Layer

A coating liquid (2) for forming an ink-receptive layer was prepared inthe same manner as in Example 1, except that the powder of the cationichydrated metal compound-supported fibrous crystalline particles (2) wasused.

Preparation of Recording Sheet (2)

Subsequently, the coating liquid was applied onto a PET film by the useof a bar coater, dried and then subjected to heat treatment at 140° C.to prepare a recording sheet (2). The ink-receptive layer had athickness of 30 μm. Then, printing was carried out on the resultingrecording sheet in the same manner as in Example 1, and the print wasevaluated.

The results are set forth in Table 1.

Example 3 Preparation of Coating Liquid (3) for Forming Ink-ReceptiveLayer

A coating liquid (3) for forming an ink-receptive layer was prepared inthe same manner as in Example 1, except that 91 parts by weight of adispersion obtained by dispersing the powder of the cationic hydratedmetal compound-supported fibrous crystalline particles (1) in water sothat the solids concentration should become 11.4% by weight and 9 partsby weight of a polyvinyl alcohol aqueous solution having a concentrationof 10% by weight were mixed.

Preparation of Recording Sheet (3)

Subsequently, the coating liquid was applied onto a PET film by the useof a bar coater, dried and then subjected to heat treatment at 140° C.to prepare a recording sheet (3). The ink-receptive layer had athickness of 30 μm. Then, printing was carried out on the resultingrecording sheet in the same manner as in Example 1, and the print wasevaluated.

The results are set forth in Table 1.

Example 4 Preparation of Coating Liquid (4) for Forming Ink-ReceptiveLayer

A coating liquid (4) for forming an ink-receptive layer was prepared inthe same manner as in Example 1, except that 80 parts by weight of adispersion obtained by dispersing the powder of the cationic hydratedmetal compound-supported fibrous crystalline particles (1) in water sothat the solids concentration should become 11.4% by weight and 20 partsby weight of a polyvinyl alcohol aqueous solution having a concentrationof 10% by weight were mixed.

Preparation of Recording Sheet (4)

Subsequently, the coating liquid was applied onto a PET film by the useof a bar coater, dried and then subjected to heat treatment at 140° C.to prepare a recording sheet (4). The ink-receptive layer had athickness of 30 μm. Then, printing was carried out on the resultingrecording sheet in the same manner as in Example 1, and the print wasevaluated.

The results are set forth in Table 1.

Example 5 Preparation of Cationic Hydrated Metal Compound-SupportedFibrous Crystalline Particles (5) for Forming Ink-Receptive Layer

In a 13.8 kg of pure water, 2 kg of basic magnesium sulfate (availablefrom Ube Materials Industries, Ltd., Mos Hige, solids concentration: 84%by weight, average fiber diameter: 0.75 μm, average fiber length: 12 μm)as a basic alkaline earth metal sulfate compound was dispersed toprepare a slurry. To the slurry, 468.1 g of a zirconium oxychlorideaqueous solution (available from Kanto Kagaku K.K., ZrO₃ concentration:10% by weight) as a cationic hydrated metal compound was added so thatthe molar ratio to the basic magnesium sulfate should become 0.36,followed by stirring at 25° C. for 60 minutes. Then, the solids wereseparated by filtration, dried at 110° C. for 16 hours and pulverized bya mixer (manufactured by Hitachi, Ltd., VA-W-27) to prepare a powder ofcationic hydrated metal compound-supported fibrous crystalline particles(5) for forming an ink-receptive layer. The powder of the cationichydrated metal compound-supported fibrous crystalline particles (5) hadan average fiber diameter of 0.75 μm, an average fiber length of 12 μmand a streaming potential of 18 μeq/g.

Preparation of Coating Liquid (5) for Forming Ink-Receptive Layer

86 Parts by weight of a dispersion obtained by dispersing theabove-obtained powder of the cationic hydrated metal compound-supportedfibrous crystalline particles (5) in water so that the solidsconcentration should become 11.4% by weight and 14 parts by weight of apolyvinyl alcohol aqueous solution having a concentration of 10% byweight were mixed to prepare a coating liquid (5) for forming anink-receptive layer.

Preparation of Recording Sheet (5)

Subsequently, the coating liquid (5) was applied onto a PET film by theuse of a bar coater, dried and then subjected to heat treatment at 140°C. to prepare a recording sheet (5). The ink-receptive layer had athickness of 30 μm. The pore volume of the ink-receptive layer wasmeasured by the aforesaid mercury penetration method.

Then, printing was carried out on the resulting recording sheet (5) inthe same manner as in Example 1, and the print was evaluated.

The results are set forth in Table 1.

Example 6 Preparation of Cationic Hydrated Metal Compound-SupportedFibrous Crystalline Particles (6) for Forming Ink-receptive Layer

A powder of cationic hydrated metal compound-supported fibrouscrystalline particles (6) was prepared in the same manner as in Example1, except that 2 kg of calcium silicate (available from Ube MaterialsIndustries Ltd., Zono Hige, solids concentration: 97% by weight, averagefiber diameter: 0.3 μm, average fiber length: 6 μm) was used as fibrouscrystalline particles. The powder of the cationic hydrated metalcompound-supported fibrous crystalline particles (6) had an averagefiber diameter of 0.3 μm, an average fiber length of 3 μm and astreaming potential of 12 μeq/g.

Preparation of Coating Liquid (6) for Forming Ink-Receptive Layer

86 Parts by weight of a dispersion obtained by dispersing theabove-obtained powder of the cationic hydrated metal compound-supportedfibrous crystalline particles (6) in water so that the solidsconcentration should become 11.4% by weight and 14 parts by weight of apolyvinyl alcohol aqueous solution having a concentration of 10% byweight were mixed to prepare a coating liquid (6) shown in Table 1.

Preparation of Recording Sheet (6)

Subsequently, the coating liquid (6) was applied onto a PET film by theuse of a bar coater, dried and then subjected to heat treatment at 140°C. to prepare a recording sheet (6). The ink-receptive layer had athickness of 30 μm. The pore volume of the ink-receptive layer wasmeasured by the aforesaid mercury penetration method.

Then, printing was carried out on the resulting recording sheet (6) inthe same manner as in Example 1, and the print was evaluated.

The results are set forth in Table 1.

Example 7 Preparation of Coating Liquid (7) for Forming Ink-ReceptiveLayer

A coating liquid (7) for forming an ink-receptive layer was prepared inthe same manner as in Example 6, except that 80 parts by weight of adispersion obtained by dispersing the powder of the cationic hydratedmetal compound-supported fibrous crystalline particles (6) in water sothat the solids concentration should become 11.4% by weight and 20 partsby weight of a polyvinyl alcohol aqueous solution having a concentrationof 10% by weight were mixed.

Preparation of Recording Sheet (7)

Subsequently, the coating liquid (7) was applied onto a PET film by theuse of a bar coater, dried and then subjected to heat treatment at 140°C. to prepare a recording sheet (7). The ink-receptive layer had athickness of 30 μm. The pore volume of the ink-receptive layer wasmeasured by the aforesaid mercury penetration method.

Then, printing was carried out on the resulting recording sheet (7) inthe same manner as in Example 1, and the print was evaluated.

The results are set forth in Table 1.

Example 8 Preparation of Coating Liquid (8) for Forming Ink-ReceptiveLayer

61 Parts by weight of a dispersion obtained by dispersing the particles(1) for forming an ink-receptive layer, said powder being obtained inthe same manner as in Example 1, in water so that the solidsconcentration should become 11.4% by weight, 25 parts by weight of a solobtained by diluting an alumina sol (available from Catalysts &Chemicals Industries Co., Ltd., Cataloid AS-3, average particlediameter: 200 nm, primary particle diameter: 9 nm, pseudo-boehmitealumina) with water so that the solids concentration should become 11.4%by weight and 14 parts by weight of a polyvinyl alcohol aqueous solutionhaving a concentration of 10% by weight were mixed to prepare a coatingliquid (8) for forming an ink-receptive layer.

Preparation of Recording Sheet (8)

Subsequently, the coating liquid was applied onto a PET film by the useof a bar coater, dried and then subjected to heat treatment at 140° C.to prepare a recording sheet (8). The ink-receptive layer had athickness of 30 μm. Then, printing was carried out on the resultingrecording sheet in the same manner as in Example 1, and the print wasevaluated.

The results are set forth in Table 1.

Example 9 Preparation of Coating Liquid (9) for Forming Ink-ReceptiveLayer

57 Parts by weight of a dispersion obtained by dispersing the particles(1) for forming an ink-receptive layer, said powder being obtained inthe same manner as in Example 1, in water so that the solidsconcentration should become 11.4% by weight, 29 parts by weight of adispersion obtained by diluting a silica sol (available from Catalysts &Chemicals Industries Co., Ltd., Cataloid SI-50, average particlediameter: 25 nm) with water so that the solids concentration shouldbecome 11.4% by weight and 14 parts by weight of a polyvinyl alcoholaqueous solution having a concentration of 10% by weight were mixed toprepare a coating liquid (9) for forming an ink-receptive layer.

Preparation of Recording Sheet (9)

Subsequently, the coating liquid was applied onto a PET film by the useof a bar coater, dried and then subjected to heat treatment at 140° C.to prepare a recording sheet (9). The ink-receptive layer had athickness of 30 μm. Then, printing was carried out on the resultingrecording sheet in the same manner as in Example 1, and the print wasevaluated.

The results are set forth in Table 1.

Comparative Example 1 Preparation of Coating Liquid (R1) for FormingInk-Receptive Layer

86 Parts by weight of a dispersion obtained by dispersing basicmagnesium sulfate (available from Ube Materials Industries Ltd., MosHige, solids concentration: 84% by weight, average fiber diameter: 0.75μm, average fiber length: 12 μm) in water so that the solidsconcentration should become 11.4% by weight and 14 parts by weight of apolyvinyl alcohol aqueous solution having a concentration of 11.4% byweight were mixed to prepare a coating liquid (R1).

Preparation of Recording Sheet (R1)

Subsequently, the coating liquid was applied onto a PET film by the useof a bar coater, dried and then subjected to heat treatment at 140° C.to prepare a recording sheet (R1). The ink-receptive layer had athickness of 30 μm. The pore volume of the ink-receptive layer wasmeasured by the aforesaid mercury penetration method.

Then, printing was carried out on the resulting recording sheet (R1) inthe same manner as in Example 1, and the print was evaluated.

The results are set forth in Table 1.

Comparative Example 2 Preparation of Coating Liquid (R2) for FormingInk-Receptive Layer

86 Parts by weight of a dispersion obtained by dispersing calciumsilicate (available from Ube Materials Industries Ltd., Zono Hige,solids concentration: 97% by weight, average fiber diameter: 0.3 μm,average fiber length: 3 μm) in water so that the solids concentrationshould become 11.5% by weight and 14 parts by weight of a polyvinylalcohol aqueous solution having a concentration of 10% by weight weremixed to prepare a coating liquid (R2).

Preparation of Recording Sheet (R2)

Subsequently, the coating liquid was applied onto a PET film by the useof a bar coater, dried and then subjected to heat treatment at 140° C.to prepare a recording sheet (R2). The ink-receptive layer had athickness of 30 μm. The pore volume of the ink-receptive layer wasmeasured by the aforesaid mercury penetration method.

Then, printing was carried out on the resulting recording sheet (R2) inthe same manner as in Example 1, and the print was evaluated.

The results are set forth in Table 1.

Comparative Example 3 Preparation of Coating Liquid (R3) for FormingInk-Receptive Layer

86 Parts by weight of a dispersion obtained by dispersing an alumina sol(available from Catalysts & Chemicals Industries Co., Ltd., CataloidAS-3, average particle diameter: 200 nm, primary particle diameter: 9nm, pseudo-boehmite alumina) in water so that the solids concentrationshould become 11.4% by weight and 14 parts by weight of a polyvinylalcohol aqueous solution having a concentration of 10% by weight weremixed to prepare a coating liquid (R3).

Preparation of Recording Sheet (R3)

Subsequently, the coating liquid was applied onto a PET film by the useof a bar coater, dried and then subjected to heat treatment at 140° C.to prepare a recording sheet (R3). The ink-receptive layer had athickness of 30 μm. Then, printing was carried out on the resultingrecording sheet in the same manner as in Example 1, and the print wasevaluated.

The results are set forth in Table 1.

TABLE 1 Reaction product for forming ink-receptive layer Ink-receptivelayer Supported Fibrous Inor- Fibrous crystalline particles cationStream- crystal- ganic Average Average Amount ing Film line fine fiberfiber (wt % in poten- thick- parti- parti- Pore volume diameter lengthAspect terms of tial ness cles cles Binder 30-2000 nm Type μm μm ratioType oxide) μeq/g μm wt % wt % wt % ml/g Ex. 1 A 0.75 12 16 Al 10 31 3088 12 0.25 Ex. 2 A 0.75 12 16 Al 13 42 30 88 12 0.35 Ex. 3 A 0.75 12 16Al 10 31 30 92 8 0.25 Ex. 4 A 0.75 12 16 Al 10 31 30 82 18 0.25 Ex. 5 A0.75 12 16 Zr 3 18 30 88 12 0.25 Ex. 6 B 0.3 3 10 Al 8 12 30 88 12 0.20Ex. 7 B 0.3 3 10 Al 8 12 30 82 18 0.20 Ex. 8 A 0.75 12 16 Al 10 50 30 8825 12 0.20 Ex. 9 A 0.75 12 16 Al 10 30 30 63 30 12 0.20 Comp. A 0.75 1216 Not reacted −5 30 88 1) 12 0.50 Ex. 1 Comp. B 0.3 3 10 Not reacted −530 88 1) 12 0.20 Ex. 2 Comp. Al₂O₃ 0.04 0.2 5 Not reacted 10 30 88 120.15 Ex. 3 Evaluation of print Dye ink Water Pigment ink resis- Den-Blot- Drying Den- Blot- Drying Crock- tance sity ting rate sity tingrate ing Ex. 1 AA 1.7 AA AA 1.6 AA AA AA Ex. 2 AA 1.8 AA AA 1.7 AA AA AAEx. 3 AA 1.7 AA AA 1.6 AA AA AA Ex. 4 AA 1.7 AA AA 1.6 AA AA AA Ex. 5 AA1.6 AA AA 1.5 AA AA AA Ex. 6 BB 1.5 AA AA 1.5 AA AA AA Ex. 7 BB 1.5 AAAA 1.5 AA AA AA Ex. 8 AA 1.7 AA BB 1.6 BB BB AA Ex. 9 BB 1.5 AA BB 1.5BB BB AA Comp. CC 1.1 CC AA 1.5 AA AA AA Ex. 1 Comp. CC 1.1 CC AA 1.2 AAAA AA Ex. 2 Comp. BB 1.4 CC CC 1.0 CC CC BB Ex. 3 A: basic magnesiumsulfate B: calcium silicate 1): In comparative Examples 1 to 2, eachvalue means a weight of not a reaction product but particles.

1. A recording sheet with an ink-receptive layer, comprising a substratesheet and an ink-receptive layer formed thereon, wherein theink-receptive layer comprises: (i) fibrous crystalline particles onsurfaces of which a cationic hydrated metal compound is supported,wherein the fibrous crystalline particles have an average fiber diameter(D) of 0.1 to 2 μm, an average fiber length (L) of 1 to 200 μm, and aratio (aspect ratio) of an average fiber length (L) to an average fiberdiameter (D) of 5 to 500, and (ii) a binder, wherein the fibrouscrystalline particles are particles of at least one substance selectedfrom the group consisting of basic magnesium sulfate, basic calciumsulfate, basic barium sulfate, and basic strontium sulfate.
 2. Therecording sheet with an ink-receptive layer as claimed in claim 1,wherein the cationic hydrated metal compound is a compound representedby the following formula (1) or a compound obtained from a metal saltrepresented by the following formula (2):[M₂(OH)_(n)X_((2a-n)/b)]_(m)  (1)[MX_(a/b)]_(m)  (2) wherein M is a trivalent or higher metallic cation,X is an anion, a is a valence of the metallic cation, b is a valence ofthe anion, and n and m are numbers satisfying the conditions of 1<n<5,n<2a and 1≦m.
 3. The recording sheet with an ink-receptive layer asclaimed in claim 2, wherein M of the cationic hydrated metal compound isAl³⁺.
 4. The recording sheet with an ink-receptive layer as claimed inclaim 1, which further comprises inorganic fine particles.
 5. Therecording sheet with an ink-receptive layer as claimed in claim 4,wherein the inorganic fine particles are one or more substances selectedfrom an alumina sol, an alumina gel, a silica sol, a silica gel, asilica-alumina sol, a silica-alumina gel, a zirconia sol, a zirconia geland a clay mineral.
 6. The recording sheet with an ink-receptive layeras claimed in claim 5, wherein the inorganic fine particles are analumina sol and/or an alumina gel each of which is pseudo-boehmitealumina.
 7. The recording sheet with an ink-receptive layer as claimedin claim 1, wherein the ink-receptive layer has pores having porediameters of 30 to 2000 nm, and a pore volume of the pores having porediameters of 30 to 2000 nm is in the range of 0.15 to 2.0 ml/g.
 8. Therecording sheet with an ink-receptive layer as claimed in claim 2, whichfurther comprises inorganic fine particles.
 9. The recording sheet withan ink-receptive layer as claimed in claim 3, which further comprisesinorganic fine particles.
 10. The recording sheet with an ink-receptivelayer as claimed in claim 2, wherein the ink-receptive layer has poreshaving pore diameters of 30 to 2000 nm, and a pore volume of the poreshaving pore diameters of 30 to 2000 nm is in the range of 0.15 to 2.0ml/g.
 11. The recording sheet with an ink-receptive layer as claimed inclaim 4, wherein the ink-receptive layer has pores having pore diametersof 30 to 2000 nm, and a pore volume of the pores having pore diametersof 30 to 2000 nm is in the range of 0.15 to 2.0 ml/g.
 12. The recordingsheet with an ink-receptive layer as claimed in claim 1, wherein thefibrous crystalline particles are particles of basic magnesium sulfate.